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Glaze chipping rather easily?


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Hi,

I've been using mainly 06 mayco glazes and noticed the rim's on mugs chipping rather easily. I apply 3 coats of glaze to 04 bisque and not sure why I'm having this issue. 

Chipped off pieces are often very small. I dont think it's from the surface being too smooth for glaze to attach...

Please let me know what possible issues thanks so much ! 

 

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Pictures for sure on this one. Is this before firing, after firing? If after did the base claybody chip with the glaze or just the glaze? Is this commercial glaze or a mixed from a recipe? Does it look like it fired to maturity? Lots of questions, I think we really need pictures to render a decent opinion.

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@Tsculpt, the reason we are all asking for photos of the chipping is because it could well be shivering thats happening. Shivering is when there isn't a good fit between the clay and the glaze and sharp little shards of glaze either spontaneously break off (usually on rims or edges) or it can happen when rims or edges are tapped. Shivering is obviously dangerous, especially with functional ware, can't tell without a photo if it might be that or simply chipping from a weak underfired body or glaze.

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Thanks for posting the picture, yes, that is shivering. Unfortunately there is nothing you can do to save these mugs, they would be dangerous to use and should be smashed prior to disposing of them. Shivering is the opposite of crazing, the glaze is under too much compression and flakes/chips away from the body. Since you are using a commercial glaze we can't offer a fix for the glaze recipe but you are going to need to try a different glaze or a different claybody. Clay and glaze need to "fit" each other. I'ld suggest just buying a small amount of a different line of glaze and make up some quick simple cylinders (they can just be thin and rough, don't need a base). Glaze them thickly in whatever glaze you want to test then fire as usual. Tap them with the something dense like a screwdriver handle and see what happens. Hopefully your next glaze won't have this fit issue. If you are in love with this glaze then try another clay body.

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13 hours ago, Tsculpt said:

invested so much into these glazes it would be better to switch clay at this point. 

If that's the most economical.

It very well could be a faulty batch or box of clay. Or perhaps just one of the glazes.

The bad thing is the rest of that batch may be sitting unused in a school somewhere right now, so there may be no word of it being bad.

Truth truth, with all "yes it is shivering" in mind for safety, I'm still not convinced. Since according to the text, it could still be them chipping when bumped.

No sense chasing gremlins.

Sorce

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Interesting in that it looks like underglaze was used to more solidly accent the rim area as well. Most commercial glaze folks will say they only test with all their product for compatibility. Is that Mayco underglaze?

Seems the chipped  areas have lost their underglaze  as well.

Edited by Bill Kielb
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where i order clay from suggested to gloss fire to cone 05 instead of 06 but would this really solve the issue?

also wondering if it could be an application error on my part. 

however looking into switching clay all together to find one that fits these glazes best

thanks!

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I am wondering, if you compressed the rims when throwing them, did you use a chamois or other method to compress the rim. If you used a sponge, the clay particles and grog get exposed and do not have as much body adhesion on the rim.   Just a thought,

best,

Pres

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